Formed membrane and method of making

ABSTRACT

An improved formed membrane and process of making is disclosed comprising the deposition of fine metallic fibers onto a formed substrate. The deposited fine fibers accumulate on the formed substrate to form a formed layer of membrane material. Catalytically active particles can be dispersed with the fine fibers. A nonporous mask can be applied to a portion of the formed substrate. The formed layer of membrane material is sintered for forming the formed membrane.

[0001] The benefit under 35 U.S.C. §119(e) of U.S. provisional application entitled PREFORMED MEMBRANE AND METHOD OF MAKING, Serial No. 60/294,148, filed May 29, 2001, is hereby claimed and the disclosure thereof is hereby incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] This invention relates to membranes and more particularly to an improved formed membrane and a method of making the same.

[0004] 2. Description of the Related Art

[0005] Metal filters have long been used for a variety of applications. For example, porous stainless steel filters prepared from sintered metal particulate, e.g., stainless steel powder, have found use in a variety of processes where high pressure drops are acceptable and in applications where relatively fine filtration capability must be combined with mechanical strength, resistance to high temperatures and/or resistance to chemical attack. Such applications include high temperature, high pressure, corrosive process gas filtration (solid-gas filtration), gas-gas separation, hydraulic/liquid filtration, gas burners, heat exchangers, electrodes, structural components requiring light weight and other non-filtration components requiring porosity. Still another use of such filters is in the filtration of molten resin used in the manufacture of polymeric films and fibers as, for example, polyester film.

[0006] One form of commercially available metal filters in cylindrical form is typically prepared from sheet material which is formed into a cylindrical shape and then longitudinally welded. Another form of metal fiber media filters and membranes are fabricated by processing a web structure; sintering these structures to form a media or membrane, forming these structures mechanically into shapes, then assembling the finished structure by welding the seam in the media and welding solid end-caps onto the open ends. Unfortunately, this method of manufacture results in a structure sensitive to rapid temperature change; uneven heating and cooling can ultimately result in cracking and failure of the structure adjacent the seam weld. Other drawbacks to such welded structures are solid endcaps and the welded seam reduce the effective surface area of the component and create non-uniform blow back characteristics and the inability to make relatively small diameter structures. For example, at one-half inch diameter, the welded seam occupies a significant portion of the overall surface available for filtration, limiting the onstream filter life for a given cycle.

SUMMARY OF THE INVENTION

[0007] One embodiment of the invention is a process of making a formed membrane from a multiplicity of fine metallic fibers. The process includes suspending the multiplicity of fine metallic fibers within a liquid binder, depositing the multiplicity of fine fibers onto a formed substrate to form a formed layer of membrane material, and sintering the formed layer of membrane material for sinter bonding the fine fibers to adjacent fine fibers to form the formed membrane.

[0008] Another embodiment of the invention is a process of making a composite formed membrane from a multiplicity of fine fibers. The process includes forming a substrate into a desired shape for forming a formed substrate, suspending a multiplicity of first fibers within a liquid binder, depositing the first fibers onto the formed substrate to form a first formed layer of membrane material. The process further includes suspending a multiplicity of second fibers within a liquid binder, depositing the second fibers onto the first formed layer of membrane material to form a composite formed layer of membrane material, and sintering the composite formed layer of membrane material for sinter bonding the fibers to adjacent fibers to form the formed membrane. In one embodiment, the second fibers are of a different size than the first fibers. In another embodiment, the second fibers are of a different material than the first fibers.

[0009] Another embodiment of the invention is a process of making a formed membrane from a multiplicity of fine metallic fibers. The process includes forming a porous substrate into a desired shape for forming a formed substrate, suspending the multiplicity of fine fibers within a liquid binder, applying a pressure to the liquid binder for forcing the liquid binder through the porous substrate for depositing the fine metallic fibers onto the porous substrate to form a formed layer of membrane material, and sintering the composite formed layer of membrane material for sinter bonding the fibers to adjacent fibers to form a substantially rigid formed membrane.

[0010] Another embodiment of the invention is a formed membrane formed from a multiplicity of fine fibers. The membrane includes a formed layer of membrane material formed from a multiplicity of fine fibers, and sinter bonds for bonding the multiplicity of fine fibers to adjacent fine fibers of the formed layer of membrane material for forming a substantially rigid formed membrane.

[0011] Another embodiment of the invention is a process of making a formed membrane from a multiplicity of fine fibers. The process includes forming a porous substrate into a desired shape for forming a formed substrate, applying a nonporous mask to a portion of the formed substrate, suspending a multiplicity of first fibers within a liquid binder, applying a pressure to the liquid binder for forcing the liquid binder through the porous substrate for depositing the first fibers onto the porous substrate to form a first formed layer of membrane material, and removing the nonporous mask from the formed substrate. The process further includes suspending a multiplicity of second fibers within a liquid binder applying a pressure to the liquid binder for forcing the liquid binder through the previously masked portion of the porous substrate for depositing the second fibers onto the previously masked portion of the porous substrate, and sintering the first and second formed layers of membrane material for sinter bonding the fibers to adjacent fibers to form a substantially rigid formed membrane having first and second fibers.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012]FIG. 1A is a block diagram illustrating a first process of forming a formed membrane, shown in FIGS. 2-5.

[0013]FIG. 1B is a block diagram illustrating a second process of forming a formed membrane, shown in FIGS. 6-11.

[0014]FIG. 1C is a block diagram illustrating a third process of forming a formed membrane, shown in FIGS. 12-19.

[0015]FIG. 1D is a block diagram illustrating a fourth process of forming a formed membrane, shown in FIGS. 20-25.

[0016]FIG. 2 is a side view illustrating an initial process of depositing fine fibers onto a formed porous substrate for forming a formed layer of membrane material.

[0017]FIG. 3 is a side view similar to FIG. 2 illustrating the continued process of depositing fine fibers onto the porous substrate for forming the formed layer of membrane material.

[0018]FIG. 4 is a side view illustrating the sintering of the formed layer of membrane material to form a formed membrane.

[0019]FIG. 5 is a magnified view of a portion of FIG. 4.

[0020]FIG. 6 is a side view illustrating an initial process of depositing first fine fibers onto a porous substrate for forming a first formed layer of membrane material.

[0021]FIG. 7 is a side view similar to FIG. 6 illustrating the continued process of depositing first fine fibers onto the porous substrate for forming the first formed layer of membrane material.

[0022]FIG. 8 is a side view similar to FIG. 7 illustrating the initial process of depositing the second fine fibers onto the first formed layer of membrane material for forming a second formed layer of membrane material.

[0023]FIG. 9 is a side view similar to FIG. 8 illustrating the continued process of depositing the second fine fibers onto the first formed layer of membrane material for forming the second formed layer of membrane material.

[0024]FIG. 10 is a side view illustrating the sintering of the first and second formed layers of membrane material to form a composite formed membrane.

[0025]FIG. 11 is a magnified view of a portion of FIG. 10.

[0026]FIG. 12 is a side view illustrating the application of a nonporous mask to a portion of the formed substrate.

[0027]FIG. 13 is a side view illustrating an initial process of depositing first fine fibers onto a porous substrate for forming a first formed layer of membrane material.

[0028]FIG. 14 is a side view similar to FIG. 13 illustrating the continued process of depositing first fine fibers onto the porous substrate for forming the first formed layer of membrane material.

[0029]FIG. 15 is a side view similar to FIG. 14 illustrating the removal of the nonporous mask from the formed substrate.

[0030]FIG. 16 is a side view similar to FIG. 15 illustrating the initial process of depositing second fine fibers onto the porous substrate within void formed in the first formed layer of membrane material by the nonporous mask.

[0031]FIG. 17 is a side view similar to FIG. 16 illustrating the continued process of depositing the second fine fibers onto the porous substrate within void formed in the first formed layer of membrane material by the nonporous mask.

[0032]FIG. 18 is a side view illustrating the sintering of the first and second formed layers of membrane material to form a composite formed membrane.

[0033]FIG. 19 is a magnified view of a portion of FIG. 18.

[0034]FIG. 20 is a side view illustrating an initial process of depositing fine fibers onto a formed porous substrate for forming a formed layer of membrane material.

[0035]FIG. 21 is a side view similar to FIG. 20 illustrating the continued process of depositing fine fibers onto the porous substrate for forming the formed layer of membrane material.

[0036]FIG. 22 illustrates the removal of the formed porous substrate and the formed layer of membrane material.

[0037]FIG. 23 illustrates the separation of the formed layer of membrane material from the formed porous substrate.

[0038]FIG. 24 is a side view of the formed layer of membrane material of the present invention. and

[0039]FIG. 25 is a top view of FIG. 24.

DETAILED DESCRIPTION OF THE INVENTION

[0040] A detailed description of an embodiment of the invention is provided below. While the invention is described in conjunction with that preferred embodiment, it should be understood that the invention is not limited to any one embodiment. On the contrary, the scope of the invention is limited only by the appended claims and the invention encompasses numerous alternatives, modifications and equivalents. For the purpose of example, numerous specific details are set forth in the following description in order to provide a thorough understanding of the invention. The invention may be practiced according to the claims without some or all of these specific details.

[0041]FIG. 1A is a block diagram illustrating a first process 5 of forming a formed membrane 10 with fine fibers 20. The first process 5 will be explained with reference to the formation of the formed membrane 10 shown in FIGS. 2-5. FIG. 1A illustrates a process step 11 of forming a formed porous substrate 25. The step of forming the formed substrate 25 includes forming the substrate 25 into a desired shape for forming a formed membrane 10 with fine fibers 20.

[0042]FIG. 2 illustrates the porous substrate 25 for forming the formed membrane 10. The formed substrate 25 is made from a porous substrate material and is formed in a desired shape to provide a pattern for the final shape of the formed membrane 10. In one embodiment of the invention, the porous substrate 25 is shown formed from a metallic mesh screen in a desired shape for the formed membrane 10. In the alternative, the porous substrate 25 may be formed from a porous ceramic material in a desired shape for the formed membrane 10.

[0043] In one embodiment of the invention, the formed substrate 25 is formed into the shape of a gas burner for a gas boiler, a gas turbine or the like. Although the formed substrate 25 has been shown in the shape of a gas burner, it should be understood that the formed substrate 25 may be formed in any suitable shape for providing a pattern for the final shape of the formed membrane 10.

[0044]FIG. 1A illustrates a process step 12 of depositing fine fibers 20 onto the formed substrate 25. The fine fibers 20 accumulate on the formed substrate 25 to form a layer of membrane material 30 of the fine fibers 20.

[0045]FIG. 2 is a side view illustrating the process step 11 of depositing the fine fibers 20 onto the formed porous substrate 25. In one embodiment, the process step 11 of depositing the fine fibers 20 onto the formed substrate 25 is accomplished within a pressure vessel 50. The pressure vessel 50 comprises a container 52 having sidewalls 54 and a base 56. A piston 58 is slidably mounted within the container 52. The formed porous substrate 25 is connected in fluid tight communication with a fluid outlet 57 defined within the base 56 of the container 52. The container 52 includes a drain valve 59 for draining a liquid from the container 52.

[0046] The fine metallic fibers 20 are suspended in a liquid binder 26. Preferably, the fine metallic fibers are metallic fibers formed by a wire drawing process and have a diameter between 0.001 microns and 100 microns. Preferably, the fine metallic fibers 20 have a diameter between 0.1 and 10 microns, and more preferably between 0.5 and 3 microns. One suitable method of drawing fine metallic fibers is explained in U.S. Pat. No. 6,112,395 entitled PROCESS OF MAKING FINE AND ULTRA FINE METALLIC FIBERS, the disclosure of which is hereby incorporated by reference in its entirety. Another method of providing fine metallic fibers using a laser is explained in U.S. Patent Application Publication No. 20020043091 entitled APPARATUS AND METHOD FOR DRAWING CONTINUOUS FIBER, the disclosure of which is hereby incorporated by reference in its entirety. The liquid binder 26 is a curable polymeric material such as an acrylic or any other suitable binder material. However, one skilled in that art will understand that the liquid binder 26 may be of any suitable type depending on the type of the fine metallic fibers 20 used to form the tubular membrane 10. The multiplicity of fine metallic fibers 20 are suspended within the liquid binder 26 and placed within the pressure vessel 50 to overlay the porous substrate 25.

[0047] In one embodiment, the fine metallic fibers can be made from stainless steel. In other embodiments, the metallic fibers can be made from FeCrAl, 17-4PH or other corrosion resistant metals. The metallic fibers can also be made from of a catalytically active material. In an alternative embodiment, the metallic fibers include fibers made from a base metal clad with a catalytic metal on the surface. For example, the fiber can have a base of 300 series stainless steel with a platinum surface. Other catalytic metals, such as cobalt, nickel and the like, can also be used.

[0048]FIG. 3 illustrates a layer of membrane material 30 of the fine fibers 20 onto the porous substrate 25 formed when substantially all of the liquid binder 26 has passed through the fluid outlet 57 defined within the base 56. A pressure is applied to the liquid binder 26 for forcing the liquid binder 26 through the porous substrate 25 for depositing the fine fibers 20 onto the formed porous substrate 25. In one embodiment, the pressure applied to the liquid binder 26 is a mechanical pressure applied by the piston 58 against the liquid binder 26 as shown by the arrow. In the alternative, a gas pressure (not shown) may be applied to the liquid binder 26 for forcing the liquid binder 26 through the porous substrate 25 for depositing the fine fibers 20 onto the porous substrate 25. In still a further alternative, a vacuum applied to the fluid outlet 57 defined in the porous base 56 of the pressure vessel 50 enables atmospheric pressure to force the liquid binder 26 through the porous substrate 25.

[0049] As explained above, the layer of membrane material 30 is formed in the shape of the formed porous substrate 25. Initially, the liquid binder 26 migrates through the formed porous substrate 25 in accordance with the shape and the flow characteristics of the container 52. After a partial accumulation of the fine fibers 20 onto the surface of the formed porous substrate 25, the liquid binder 26 migrates preferentially through the areas of least accumulation of the fine fibers 20 onto the surface of the formed porous substrate 25. This pressure wet lay process results in a substantially uniform porosity to the layer of membrane material 30.

[0050] The thickness and the porosity of the layer of membrane material 30 of the fine fibers 20 may be preselected by controlling various parameters during the process step 12 of depositing fine fibers 20 onto the formed substrate 25. These various parameters include the control of the volume of the liquid binder 26, the density of the fine fibers 20 within the liquid binder 26, the rate of movement of the piston 58, the pressure applied to the piston 58 and the flow rate of the liquid binder 26 through the formed porous substrate 25.

[0051]FIG. 3 illustrates a substantial portion of the liquid binder 26 passing through the fluid outlet 57. The multiplicity of fine fibers 20 accumulate on the formed porous substrate 25 for forming the layer of membrane material 30. After the liquid binder 26 has passed through the formed porous substrate 25, the formed porous substrate 25 supports the layer of membrane material 30 of the fine fibers 20 coated with the remainder of the liquid binder 26. The layer of membrane material 30 of the fine fibers 20 supported by the formed porous substrate 25 is removed from the pressure vessel 50.

[0052] In one embodiment of the invention, the layer of membrane material 30 of the fine fibers 20 remains on the formed porous substrate 25. In an alternative embodiment of the invention, the layer of membrane material 30 of the fine fibers 20 is removed from the formed porous substrate 25. The liquid binder 26 maintains the integrity of the layer of membrane material 30 of the fine fibers 20 after removal from the formed porous substrate 25.

[0053] The layer of membrane material 30 of the fine fibers 20 is allowed to dry or cure either in an atmospheric condition or in a drying oven or the like. The cured liquid binder 26 maintains the integrity of the layer of membrane material 30 of the fine fibers 20.

[0054] In still a further alternative embodiment of the invention, the layer of membrane material 30 of the fine fibers 20 may be heated in an oven prior to removal from the formed porous substrate 25. The layer of membrane material 30 is heated for a time and temperature sufficient to liberate the cured liquid binder 26 from the fine fibers 20. In one embodiment, the layer of membrane material 30 of the fine fibers 20 is heated for a time sufficient for the fine fibers 20 to adhere to an adjacent fine fiber 20 to form a flexible layer of membrane material 30. The flexible layer of membrane material 30 facilitates the removal of the layer of membrane material 30 from the formed porous substrate 25.

[0055] In one example, heating the layer of membrane material 30 made of stainless steel fibers 20 having a diameter of 2.0 microns at temperature 212 degrees Fahrenheit for a period of 20 hours within an air atmosphere provides a suitable flexible layer of membrane material 30.

[0056] In one embodiment, a catalytically active material can be dispersed with the fine fibers 20. The catalytically active material can be dispersed into the fine metallic fibers 20 before the fibers 20 are deposited onto the porous substrate 25. Alternately, a catalyically active material can be injected into the pores of the membrane material 30. The catalytically active material may be injected or dispersed by an air injection lay process or a wet lay injection process. In addition, the catalytically active material may be injected and dispersed by a pasting process.

[0057]FIG. 1A illustrates a process step 13 of sintering the layer of membrane material 30 of the fine fibers 20 to form the formed membrane 10. The sintering of the layer of membrane material 30 of the fine fibers 20 transforms the layer of membrane material 30 into a substantially rigid formed membrane 10.

[0058]FIG. 4 is a side view illustrating the process step 13 of sintering of the layer of membrane material 30 of the fine fibers 20 to form the formed membrane 10. In one embodiment, the layer of membrane material 30 of the fine fibers 20 is passed through a sintering chamber 60. The sintering chamber 60 includes an upper and a lower heater 61 and 62. The sintering chamber 60 may contain a specialized atmosphere such as an inert atmosphere or a reducing atmosphere depending upon the type of fine fibers 20 used for making the formed membrane 10 of the present invention. Furthermore, the process step 13 of sintering the layer of membrane material 30 may take place as a continuous process or as a batch process as should be well known to those skilled in the art.

[0059] The process step 13 of sintering the layer of membrane material 30 utilizes a higher temperature than the heating of membrane material 30 previously set forth. In one embodiment, the layer of membrane material 30 is heated for time sufficient for the fine fibers 20 to sinter bond with adjacent fine fibers 20. The sinter bond between adjacent fine fibers 20 provides a substantially rigid formed membrane 10. In one example, a rigid formed membrane 10 made of stainless steel fibers 20 having a diameter of 2.0 microns is sintered at a temperature of 1750 degrees Fahrenheit for a period of one hour within a partial hydrogen atmosphere to provide a suitable formed membrane 10. The membrane 10 can be heated at a temperature between 1300 and 2150 degrees Fahrenheit, with the lower sintering temperatures used with smaller fibers. One skilled in the art will understand that other methods of sintering can be used such as induction sintering and infrared sintering such as is taught in U.S. Pat. No. 6,200,523 entitled APPARATUS AND METHOD OF SINTERING ELEMENTS BY INFRARED HEATING, the disclosure of which is hereby incorporated by reference in its entirety.

[0060]FIG. 5 is a magnified sectional view of a portion of FIG. 4 illustrating the sidewall of the formed membrane 10. In one embodiment, the formed membrane 10 comprises the formed porous substrate 25 sinter bonded to support the layer of membrane material 30. The formed porous substrate 25 may be provided with a mounting ferrule (not shown) for mounting the formed membrane 10.

[0061]FIG. 1B is a block diagram illustrating a second process 105 of forming a formed membrane 110 with first and second fine fibers 121 and 122. The second process 105 will be explained with the reference to the formation of the formed membrane 110 shown in FIGS. 6-11.

[0062]FIG. 1B illustrates a process step 111 of forming a formed substrate 125. The formed substrate 125 is formed into a desired shape for forming a formed membrane 110 with first and second fine fibers 121 and 122. The first and second fine fibers 121 and 122 can be made from stainless steel. In other embodiments, the metallic fibers can be made from FeCrAl, 17-4PH or other corrosion resistant metals. The metallic fibers can also be made from of a catalytically active material. In an alternative embodiment, the metallic fibers include fibers made from a base metal clad with a catalytic metal on the surface. For example, the fiber can have a base of 300 series stainless steel with a platinum surface. Other catalytic metals, such as Cobalt, Nickel and the like, can also be used.

[0063]FIG. 6 illustrates a porous substrate 125 in a desired shape for forming a formed membrane 110 with first and second fine fibers 121 and 122. The porous substrate 125 is shown formed from a porous ceramic material but the porous substrate 125 may be formed from a metallic mesh screen as previously set forth. Although the formed substrate 125 has been shown in the shape of a gas burner, it should be understood that the formed substrate 125 may be formed in any suitable shape for providing a pattern for the final shape of the formed membrane 110.

[0064]FIG. 1B illustrates a process step 112 of depositing first fine fibers 121 onto the formed substrate 125 to form a first layer of membrane material 131 of the first fine fibers 121.

[0065]FIG. 6 is a side view illustrating the process step 112 of depositing the first fine fibers 121 onto the formed porous substrate 125. The process step 112 of depositing the first fine fibers 121 onto the formed substrate 125 is accomplished within a pressure vessel 50 as described previously. Catalytically active material can be dispersed with the fine fibers as previously set forth.

[0066]FIG. 7 is a side view similar to FIG. 6 illustrating the process step 112 of depositing the first fine fibers 121 onto the porous substrate 125. The pressure applied to the liquid binder 126 forces the liquid binder 126 through the formed porous substrate 125 for depositing the first fine fibers 121 onto the formed porous substrate 125.

[0067] The process step 112 of depositing the first fine fibers 121 onto the porous substrate 125 is terminated after an appropriate thickness of the first layer of membrane material 131 of the first fine fibers 121 is deposited onto the formed porous substrate 125. The remaining liquid binder 126 and first fine fibers 121 not deposited onto the porous substrate 125 are removed from the container 50 through the outlet valve 59.

[0068]FIG. 1B illustrates a process step 113 of depositing the second fine fibers 122 onto the first layer of membrane material 131. The second fine fibers 122 are deposited onto the first layer of membrane material 131 in a manner similar to the process step 112 of depositing first fine fibers 121 on the formed substrate 125. The second fine fibers 122 accumulate on the first layer of membrane material 131 to form a second layer of membrane material 132 of the second fine fibers 122.

[0069]FIG. 8 is a side view illustrating an initial process 113 of depositing the second fine fibers 122 onto the first layer of membrane material 131. The process step 113 of depositing the second fine fibers 122 onto the first layer of membrane material 131 is accomplished within a pressure vessel 50 as described previously.

[0070]FIG. 9 is a side view similar to FIG. 8 illustrating the continued process step 113 of depositing the second fine fibers 122 onto the first layer of membrane material 131. The pressure applied to the liquid binder 126 forces the liquid binder 126 through the first layer of membrane material 131 and through the formed porous substrate 125 for depositing the second fine fibers 122 onto the first layer of membrane material 131.

[0071] The process step 113 of depositing the second fine fibers 122 onto the first layer of membrane material 131 is terminated after an appropriate thickness of the second layer of membrane material 132 is deposited onto the first layer of membrane material 131 to form a composite membrane material 133. The composite membrane material 133 may remain on the formed porous substrate 125 or may be removed from the formed porous substrate 125 as set forth previously.

[0072] Preferably, the first fine fibers 121 are different from the second fine fibers 122. In one embodiment, the first fine fibers 121 have a different fiber diameter or thickness than the second fine fibers 122. In another embodiment, the first fine fibers 121 are made from a different material than the second fine fibers 122.

[0073]FIG. 1B illustrates a process step 114 of sintering the composite layer of membrane material 133 of the first and second fine fibers 121 and 122 to form the formed membrane 110. The sintering of the composite layer of membrane material 133 of the first and second fine fibers 121 and 122 transforms the composite layer of membrane material 133 into a substantially rigid formed membrane 110.

[0074]FIG. 10 is a side view illustrating the process step 114 of sintering the composite layer of membrane material 133 of the first and second fine fibers 121 and 122 to form the formed membrane 110. In one embodiment, the composite layer of membrane material 133 is passed through the sintering chamber 60 as described previously. After the sintering process the first and second layers of the membrane material 131 and 132 are bonded into the composite membrane 133.

[0075]FIG. 11 is a magnified sectional view of a portion of FIG. 10 illustrating the sidewall of the formed membrane 110. In one embodiment, the formed membrane 110 comprises the composite layer of membrane material 133. The first layer of membrane material 131 is supporting the second layer of membrane material 132. The first layer of membrane material 131 may be provided with a mounting ferrule for mounting the formed membrane 110.

[0076]FIG. 1C is a block diagram illustrating a third process 205 of forming a formed membrane 210 with first and second fine fibers 221 and 222. The third process 205 will be explained with reference to the formation of the formed membrane 210 shown in FIGS. 12-19.

[0077]FIG. 1C illustrates a process step 211 of forming a formed substrate 225. The formed substrate 225 is formed into a desired shape for forming a formed membrane 210 with the first and second fine fibers 221 and 222.

[0078]FIG. 12 illustrates a porous substrate 225 into a desired shape for forming a formed membrane 210 with first and second fine fibers 221 and 222. The porous substrate 225 is shown formed from a metallic mesh screen. Catalytically active material can be dispersed with the fine fibers as previously set forth.

[0079]FIG. 1C illustrates the process step 212 of applying a nonporous mask 241 to selected portions of the formed substrate 225. The nonporous mask 241 may be made of any suitable material such as a polymeric material, a metallic material or the like.

[0080]FIG. 12 illustrates a porous substrate 225 with the nonporous mask 241 secured to selected portions of the formed substrate 225. In one embodiment, the nonporous mask 241 comprised a flexible polymeric material having a suitable adhesive for securing to the formed substrate 225. It should be appreciated by those skilled in the art that many other types of materials may be used for the nonporous mask 241.

[0081]FIG. 1C illustrates a process step 213 of depositing first time fibers 221 onto the formed substrate 225. The first fine fibers 221 are deposited onto the formed substrate 225. The first fine fibers 221 accumulate on the formed substrate 225 to form a first layer of membrane material 231 of the first fine fibers 221.

[0082]FIG. 13 is a side view illustrating an initial process 213 of depositing the first fine fibers 221 onto a formed porous substrate 225. The process step 213 of depositing the first fine fibers 221 onto the formed substrate 225 is accomplished within the pressure vessel 50 as described previously.

[0083] The nonporous mask 241 blocks the flow of the liquid binder 226 through the formed substrate 225 at the selected portions of the formed substrate 225. The nonporous mask 241 inhibits the deposition of the first fine fibers 221 onto the selected portions of the formed substrate 225.

[0084]FIG. 14 is a side view similar to FIG. 13 illustrating the continued process step 213 of depositing the first fine fibers 221 onto the porous substrate 225. The pressure applied to the liquid binder 226 forces the liquid binder 226 through the formed porous substrate 225 for depositing the first fine fibers 221 onto the formed porous substrate 225. The nonporous mask 241 blocks the flow of the liquid binder 226 through the formed substrate 225 at the selected portions of the formed substrate 225.

[0085] The process step 213 of depositing the first fine fibers 221 onto the porous substrate 225 is terminated after an appropriate thickness of the first layer of membrane material 231 of the first fine fibers 221 is deposited onto the formed porous substrate 225. The remaining liquid binder 226 and first fine fibers 221 are removed from the container 50 through the outlet valve 59.

[0086]FIG. 1C illustrates a process step 214 of removing the nonporous mask 241 from the selected portions of the formed substrate 225. After removal of the nonporous mask 241, the formed substrate 225 is exposed at the selected portions of the formed substrate 225.

[0087]FIG. 15 illustrates a porous substrate 225 with the nonporous mask 241 removed to expose the selected portions of the formed substrate 225. The nonporous mask 241 may be readily removed from the selected portions of the formed substrate 225 when an adhesive is used to secure the nonporous mask 241 to the formed substrate 225. A strong adhesive is not needed since the pressure applied to the liquid binder 226 assists the adhesive in maintaining the position of the nonporous mask 241 on the formed substrate 225.

[0088]FIG. 1C illustrates a process step 215 of depositing second fine fibers 222 onto the selected portions of the formed substrate 225 and subsequently onto the first layer of membrane material 231 of the first fine fibers 221. Initially, the second fine fibers 222 are preferentially deposited onto the selected portions of the formed substrate 225. The second fine fibers 222 accumulate at the selected portions of the formed substrate 225 to form a second layer of membrane material 232 of the second fine fibers 222. Thereafter, the second fine fibers 222 are deposited onto the first layer of membrane material 231 of the first fine fibers 221 to form a second layer of membrane material 232.

[0089]FIG. 16 is a side view illustrating an initial process 215 of depositing the second fine fibers 222 onto the selected portions of the formed substrate 225. The process step 215 of depositing the second fine fibers 222 onto the selected portions of the formed substrate 225 is accomplished within the pressure vessel 50 as described previously.

[0090]FIG. 17 is a side view similar to FIG. 16 illustrating the continued process step 215 of depositing the second fine fibers 222 onto the selected portions of the formed substrate 225 and subsequently onto the first layer of membrane material 231 of the first fine fibers 221. The pressure applied to the liquid binder 126 forces the liquid binder 126 through the previously masked portion 241 of the formed porous substrate 225 for depositing the second fibers 222 onto the previously masked 241 of the porous substrate 225. The second fine fibers 222 are preferentially deposited onto the previously masked portions 241 of the formed substrate 225. Thereafter, the second fine fibers 222 are deposited onto the first layer of membrane material 231 of the first fine fibers 221 to form a second layer of membrane material 232.

[0091] The process step 215 of depositing the second fibers 222 onto the first layer of membrane material 231 is terminated after an appropriate thickness of the second layer of membrane material 232 is deposited onto the first layer of membrane material 231 to form a composite membrane material 233. The composite membrane material 233 may remain on the formed porous substrate 225 or may be removed from the formed porous substrate 225 as set forth previously.

[0092] Preferably, the first fibers 221 are different from the second fibers 222. In one embodiment, the first fibers 221 have a different fiber diameter or thickness than the second fibers 222. In another embodiment, the first fibers 221 are made from a different material than the second fibers 222.

[0093]FIG. 1C illustrates a process step 216 of sintering the composite layer of membrane material 233 of the first and second fine fibers 221 and 222 to form the formed membrane 210. The sintering of the composite layer of membrane material 233 of the first and second fine fibers 221 and 222 transforms the composite layer of membrane material 233 into a substantially rigid formed membrane 210.

[0094]FIG. 18 is a side view illustrating the process step 216 of sintering of the composite layer of membrane material 233 of the first and second fibers 221 and 222 to form the formed membrane 210. In one embodiment, the composite layer of membrane material 233 is passed through the sintering chamber 60 as described previously. After the sintering process, the first and second layers of the membrane material 231 and 232 are bonded into the composite membrane 233.

[0095]FIG. 19 is a magnified section view of a portion of FIG. 18 illustrating the sidewall of the formed membrane 210. In one embodiment, the formed membrane 210 comprises the composite layer of membrane material 233 comprising the first and second layers of the membrane material 231 and 232. The first layer membrane of the material 231 overlays all of the formed substrate 225 except the masked portions 241. The second layer of the membrane material 232 overlays the masked portions 241 and overlays the first layer of the membrane material 231.

[0096]FIG. 1C illustrates alternative process steps 214A and 215A for the third process 205 of forming a formed membrane 210 with first and second fine fibers 221 and 222. The alternative third process 205 will be explained with reference to the formation of the formed membrane 210A shown in FIGS. 16A-19A.

[0097]FIG. 1C illustrates the alternate process step 214A of applying a second nonporous mask 241 to the first layer of membrane material 231A of the first fine fibers 221. The second nonporous mask 242 may be made of any suitable material such as a polymeric material, a metallic material or the like as set forth previously.

[0098]FIG. 1C illustrates the process step 215 of depositing second fine fibers 222 onto only the selected portions of the formed substrate 225. The second fine fibers 222 are deposited only onto the selected portions of the formed substrate 225 to form a second layer of membrane material 232A of the second fine fibers 222.

[0099]FIG. 16A is a side view illustrating an initial process 215 of depositing the second fine fibers 222 only onto the selected portions of the formed substrate 225. The process step 215 of depositing the second fine fibers 222 onto the selected portions of the formed substrate 225 is accomplished within the pressure vessel 50 as described previously. Catalytically active material can be dispersed with the fine fibers as previously set forth.

[0100]FIG. 17A is a side view similar to FIG. 16A illustrating the continued process step 215 of depositing the second fine fibers 222 onto only the selected portions of the formed substrate 225. The pressure applied to the liquid binder 126 forces the liquid binder 126 through the previously masked portion 241 of the formed porous substrate 225 for depositing the second fibers 222 only onto the previously masked portion 241 of the porous substrate 225. The second nonporous mask 242 overlays the first layer of membrane material 231A of the first fine fibers 221 and prevents the accumulation of the second fine fibers 222 onto the first layer of membrane material 231A.

[0101] The process step 215 of depositing the second fibers 222 is terminated after an appropriate thickness of the second layer of membrane material 232 is deposited onto the previously masked portion 241 to form a composite membrane material 233A.

[0102]FIG. 1C illustrates then alternate process step 215A of removing the second nonporous mask 242 from the first layer of membrane material 231A. The second nonporous mask 242 may be readily removed from the first layer of membrane material 231A as previously described.

[0103]FIG. 18A is a side view illustrating the process step 216 of sintering of the composite layer of membrane material 233A of the first and second fibers 221 and 222 to form the formed membrane 210A. In one embodiment, the composite layer of membrane material 233A is passed through the sintering chamber 60 as described previously. After the sintering process, the first and second layers of the membrane material 231A and 232A are bonded into the composite membrane 233A.

[0104]FIG. 19A is a magnified sectional view of a portion of FIG. 18 illustrating the sidewall of the formed membrane 210A. In one embodiment, the formed membrane 210A comprises the composite layer of membrane material 233A comprising the first and second layers of the membrane material 231A and 232A. The first layer membrane of the material 231A overlays the formed substrate 225 except the masked portions 241. The second layer of the membrane material 232A overlays only the masked portions 241.

[0105]FIG. 1D is a block diagram illustrating a fifth process 305 of forming a formed membrane 310 with fine fibers 320. The fifth process 305 will be explained with reference to the formation of the formed membrane 310 shown in FIGS. 20-25. FIG. 1D illustrates a process step 311 of forming a formed substrate 325 into a desired shape for forming a formed membrane 310 with fine fibers 320.

[0106]FIG. 20 illustrates a porous substrate 325 for forming a formed membrane 310 with fine fibers 320. In one embodiment of the invention, the porous substrate 325 is shown having a cylindrical shape defining an inner cylindrical surface 329. Preferably, the porous substrate 325 is formed from a porous ceramic material.

[0107]FIG. 1D illustrates a process step 312 of depositing fine fibers 320 onto the formed substrate 325. The fine fibers 320 accumulate on the formed substrate 325 to form a layer of membrane material 330 of the fine fibers 320.

[0108]FIG. 20 is a side view illustrating an initial process 312 of depositing the fine fibers 320 onto a formed porous substrate 325. A pressure vessel 350 comprises a container 352 having sidewalls 354 and a base 356. A piston 358 is slidably mounted within the container 352. The sidewalls 354 includes a porous sidewall portion 357. The formed substrate 325 is connected in fluid tight communication with the porous sidewall portion 357 of the container 352.

[0109] In one embodiment of the invention, the fine fibers 320 are suspended in a liquid binder 326. The liquid binder 326 may be of any suitable type depending on the type of the fine fibers 320 used to form the formed membrane 310.

[0110]FIG. 21 is a side view similar to FIG. 20 illustrating the continued process step 312 of depositing the fine fibers 320 onto the porous substrate 325. A pressure is applied to the liquid binder 326 for forcing the liquid binder 326 through the formed porous substrate 325 for depositing the fine fibers 320 onto the formed porous substrate 325. The fine fibers 320 are deposited on the inner cylindrical surface 329 of the formed porous substrate 325. The multiplicity of fine fibers 320 accumulate on the inner cylindrical surface 329 of the formed porous substrate 325 for forming the layer of membrane material 30.

[0111]FIG. 1D illustrates the process step 313 of shrinking the layer of membrane material 330. After the liquid binder 326 has passed through the formed porous substrate 325, the formed porous substrate 325 supports the layer of membrane material 330 of the fine fibers 320. The formed porous substrate 325 and the layer of membrane material 330 of the fine fibers 320 are removed from the pressure vessel 350.

[0112]FIG. 22 illustrates removal of the formed porous substrate 325 and the layer of membrane material 330 of the fine fibers 320 from the pressure vessel 350. The layer of membrane material 330 of the fine fibers 320 is supported by the formed porous substrate 325.

[0113]FIG. 23 illustrates the separation of the layer of membrane material 330 of the fine fibers 320 from the formed porous substrate 325. The layer of membrane material 330 of the fine fibers 320 is allowed to dry or cure on the formed porous substrate 325 either in an atmospheric condition or in a drying oven or the like. As the layer of membrane material 330 of the fine fibers 320 is allowed to dry or cure, the layer of membrane material 330 shrinks and separates from the formed porous substrate 325.

[0114]FIGS. 24 and 25 illustrate the layer of membrane material 330 of the fine fibers 320 removed from the formed porous substrate 325. The layer of membrane material 330 is sintered in a manner similar to the sintering as set forth previously.

[0115] The process of the present invention has many applications and uses as should be appreciated by those skilled in the art. The following is a small list of applications and uses of the present invention, but this should not be construed to be a complete or exhaustive list of applications and uses.

[0116] The present invention may be used in burners for natural gas turbine electricity generating plants, mantels for propane lanterns and for other gas burners such as propane and the like. The burners may be shaped for providing shaped burner surfaces. The present invention may be used in filters such as air conditioning filters, fuel filters and the like. The present invention may be used as a support for catalytic converters or skeleton for filters made from otherwise weak fibers. The present invention may be used as a substrate for a catalyst. The present invention may be used as diffusers and electrical electrodes for electrochemical operations, batteries, fuel cells and the like. The present invention may be used in heat exchangers and the like.

[0117] Specific blocks, sections, devices, functions and modules have been set forth. However, a skilled technologist will recognize that there are many ways to partition the system of the invention, and that there are many parts, components, modules or functions that may be substituted for those listed above. While the above detailed description has shown, described, and pointed out fundamental novel features of the invention as applied to various embodiments, it will be understood that various omissions and substitutions and changes in the form and details of the system illustrated may be made by those skilled in the art, without departing from the intent of the invention. 

What is claimed is:
 1. A process of making a formed membrane from a multiplicity of fine metallic fibers, comprising: suspending the multiplicity of fine metallic fibers within a liquid binder; depositing the multiplicity of fine fibers onto a formed substrate to form a formed layer of membrane material; and sintering the formed layer of membrane material for sinter bonding the fine fibers to adjacent fine fibers to form the formed membrane.
 2. A process of making a formed membrane as set forth in claim 1, further comprising dispersing a catalytically active material into the multiplicity of fine metallic fibers.
 3. A process of making a formed membrane as set forth in claim 1, further comprising applying a nonporous mask to a portion of the formed substrate.
 4. A process of making a formed membrane as set forth in claim 1, wherein the fine fibers are made by a metallic wire drawing process.
 5. A process of making a formed membrane as set forth in claim 1, wherein the liquid binder is a curable polymeric material.
 6. A process of making a formed membrane as set forth in claim 1, wherein the fine fibers are deposited onto a formed porous substrate comprising a mesh material.
 7. A process of making a formed membrane as set forth in claim 1, wherein the fine fibers are deposited onto a formed porous substrate comprising a ceramic material.
 8. A process of making a formed membrane as set forth in claim 1, further comprising removing the formed layer of membrane material from the porous substrate.
 9. A process of making a formed membrane as set forth in claim 1, further comprising: heating the formed layer of membrane material for a time sufficient for adhering the fine fibers to adjacent fine fibers; and removing the formed layer of membrane material from the porous substrate prior to sintering the formed layer of membrane material.
 10. A process of making a formed membrane as set forth in claim 1, wherein sintering the formed layer of membrane material comprises sintering the layer of membrane material and the formed substrate for a time sufficient for sinter bonding the fine fibers to adjacent fine fibers.
 11. A process of making a formed membrane as set forth in claim 1, wherein sintering the formed layer of membrane material comprises sintering the layer of membrane material for a time sufficient for forming a substantially rigid formed membrane.
 12. A process of making a formed membrane as set forth in claim 1, wherein sintering the formed layer of membrane material comprises sintering the layer of membrane material and the substrate for a time sufficient for sinter bonding the fine fibers to adjacent fine fibers and for sinter bonding fine fibers to the porous substrate.
 13. A process of making a formed membrane from a multiplicity of fine fibers, comprising: forming a substrate into a desired shape for forming a formed porous substrate; suspending the multiplicity of fine fibers within a liquid binder; depositing the fine fibers onto the formed substrate to form a formed layer of membrane material; and sintering the formed layer of membrane material for sinter bonding the fine fibers to adjacent fine fibers to form the formed membrane.
 14. A process of making a formed membrane as set forth in claim 13, wherein the liquid binder is a curable liquid binder.
 15. A process of making a formed membrane as set forth in claim 13, further comprising applying a pressure to the liquid binder for depositing the fine metallic fibers onto the formed porous substrate.
 16. A process of making a formed membrane as set forth in claim 15, wherein the pressure is a mechanical pressure.
 17. A process of making a formed membrane as set forth in claim 16, wherein the mechanical pressure is applied with a piston.
 18. A process of making a formed membrane as set forth in claim 17, wherein the piston a hydraulically operated piston.
 19. A process of making a formed membrane as set forth in claim 13, further comprising: heating the formed layer of membrane material for a time sufficient for adhering the fine fibers to adjacent fine fibers; and removing the formed layer of membrane material from the formed porous substrate prior to the process of sintering the formed layer of membrane material.
 20. A process of making a composite formed membrane from a multiplicity of fine fibers, comprising: forming a substrate into a desired shape for forming a formed substrate; suspending a multiplicity of first fibers within a liquid binder; depositing the first fibers onto the formed substrate to form a first formed layer of membrane material; suspending a multiplicity of second fibers within a liquid binder; depositing the second fibers onto the first formed layer of membrane material to form a composite formed layer of membrane material; and sintering the composite formed layer of membrane material for sinter bonding the fibers to adjacent fibers to form the formed membrane.
 21. A process of making a formed membrane as set forth in claim 20, wherein the second fibers are of a different size than the first fibers.
 22. A process of making a formed membrane as set forth in claim 20, wherein the second fibers are of a different material than the first fibers.
 23. A process of making a formed membrane from a multiplicity of fine metallic fibers, comprising: forming a porous substrate into a desired shape for forming a formed substrate; suspending the multiplicity of fine fibers within a liquid binder; applying a pressure to the liquid binder for forcing the liquid binder through the porous substrate for depositing the fine metallic fibers onto the porous substrate to form a formed layer of membrane material; and sintering the composite formed layer of membrane material for sinter bonding the fibers to adjacent fibers to form a substantially rigid formed membrane.
 24. A process of making a composite formed membrane from a multiplicity of fine fibers, comprising: forming a porous substrate into a desired shape for forming a formed substrate; suspending a multiplicity of first fibers within a liquid binder; applying a pressure to the liquid binder for forcing the liquid binder through the porous substrate for depositing the first fibers onto the porous substrate to form a first formed layer of membrane material; suspending a multiplicity of second fibers within a liquid binder; applying a pressure to the liquid binder for forcing the liquid binder through the first formed layer of membrane material and the porous substrate for depositing the second fibers onto the first formed layer of membrane material to form a composite formed layer of membrane material; and sintering the composite formed layer of membrane material for sinter bonding the fibers to adjacent fibers to form a substantially rigid formed membrane having overlaying layers of the first and second fibers.
 25. A process of making a formed membrane as set forth in claim 24, wherein the second fibers are of a different size than the first fibers.
 26. A process of making a formed membrane as set forth in claim 24, wherein the second fibers are of a different material than the first fibers.
 27. A process of making a formed membrane from a multiplicity of fine fibers, comprising: forming a porous substrate into a desired shape for forming a formed substrate; applying a nonporous mask to a portion of the formed substrate; suspending a multiplicity of first fibers within a liquid binder; applying a pressure to the liquid binder for forcing the liquid binder through the porous substrate for depositing the first fibers onto the porous substrate to form a first formed layer of membrane material; removing the nonporous mask from the formed substrate; suspending a multiplicity of second fibers within a liquid binder; applying a pressure to the liquid binder for forcing the liquid binder through the previously masked portion of the porous substrate for depositing the second fibers onto the previously masked portion of the porous substrate; and sintering the first and second formed layers of membrane material for sinter bonding the fibers to adjacent fibers to form a substantially rigid formed membrane having first and second fibers.
 28. A process of making a formed membrane as set forth in claim 27, wherein the second fibers are of a different size than the first fibers.
 29. A process of making a formed membrane as set forth in claim 27, wherein the second fibers are of a different material than the first fibers.
 30. A formed membrane formed from a multiplicity of fine fibers, comprising: a formed layer of membrane material formed from a multiplicity of fine fibers; and a sinter bond for bonding said multiplicity of fine fibers to adjacent fine fibers of said formed layer of membrane material for forming a substantially rigid formed membrane.
 31. A formed membrane formed from a multiplicity of fine fibers as set forth in claim 30, wherein said fine fibers comprise fine metallic fibers.
 32. A formed membrane formed from a multiplicity of fine fibers as set forth in claim 30, wherein said fine metallic fibers have a diameter between 0.001 and 100 microns.
 33. A formed membrane formed from a multiplicity of fine fibers as set forth in claim 30, wherein said multiplicity of fine fibers are formed in a wire drawing process.
 34. A formed membrane formed from a multiplicity of fine fibers as set forth in claim 30, wherein said formed layer of membrane material is supported by a porous substrate.
 35. A formed composite membrane formed from a multiplicity of fine fibers, comprising: a first formed layer of membrane material formed from a multiplicity of first fine fibers; a second formed layer of membrane material formed from a multiplicity of second fine fibers; and sinter bonds for bonding said multiplicity of first fine fibers to adjacent first fine fibers of said first formed layer of membrane material, for bonding said multiplicity of second fine fibers to adjacent second fine fibers of said second formed layer of membrane material, and for bonding said first formed layer of membrane material to said second formed layer of membrane material for forming a substantially rigid formed composite membrane.
 36. A formed composite membrane formed from a multiplicity of fine fibers as set forth in claim 35, wherein said second formed layer of membrane material overlies said first formed layer of membrane material.
 37. A formed composite membrane formed from a multiplicity of fine fibers as set forth in claim 35, wherein said second formed layer of membrane material is located adjacent to said first formed layer of membrane material. 